Oil burner with spill return duct controllable by flow reversal



April 24, 1956 A. W. WILSON OIL BURNER WITH SPILL RETURN DUCTCONTROLLABLE BY FLOW REVERSAL Filed July 18, 1952 \nveni'on Nan MwilsonHis Nn orneL;

United States Patent OIL BURNER WITH SPILL RETURN DUCT CONTROLLABLE BYFLOW REVERSAL Alan William Wilson, London, England, assignor to ShellDevelopment Company, Emeryville, Califl, a corporation of DelawareApplication July 18, 1952, Serial No. 299,611 Claims priority,application Great Britain August 2, 1951 11 Claims. (Cl. 299-118) Thisinvention relates to apparatus for burning liquid fuel of the typecomprising a reservoir for liquid fuel such as oil and a pump forsupplying fuel from this reservoir under pressure to one or more liquidfuelatomizing burners of the kind which comprises a prechamber, such asa vortex chamber, communicating with a fuel supply duct through one or'more ports, such as tangential ports, and with a spill return duct forreturning a variable amount of excess fuel from the vortex chamber tothe reservoir, the vortex chamber having a final outlet orifice throughwhich the fuel emerges as a spray. Apparatus of this type is hereinafterreferred to as apparatus of the type specified. The invention relatesfurther to an improved liquid fuel-atomizing burner proper, suitable foruse in the apparatus of-thetype specified- It is frequently necessary ordesirable to circulate the liquid fuel through the body of the burner toa point adjacent to the burner tip when the burner is not in operation,i. e., before the tip or orifice valve thereof is opened up, in order,for example, when heavy or highly viscous fuel is 'used, to displaceviscous cold fuel which is' left in the vortex chamber and associatedparts from a previous operation and to replace it by heated fuel whichhas a lower viscosity and is adapted to be discharged through theorifice as a well-formed spray. It

. may also be desirable to circulate fuel through the burner immediatelyafter it has been shut down, inorder to protect it from the heatradiated by the combustion chamber wall. Again, where a combustionchamber is provided with a plurality of atomizing burners, some of whichmay be shut down under conditions of light load while others are inoperation, it ,is advantageous to circulate fuel throughthe burners thatare shut down in order to cool them and thereby avoid damage to themfrom the intense radiationof the flames from the other burners or of therefractory in the combustion chamber.

In order to enable the fuel to be circulated through the atomizingburner when the latter is not in operation, it has heretofore beenproposedto provide the burner with a tip or orifice valve which can beoperated manually to close the final orifice, thus allowing fuelto becirculated through the, fuel supply duct, vortex chamber and spillreturn duct in sequence without issuing from the final orifice. Manualoperation of the tip valve, however, involves structural complication,especially where the rear end of the burner is enclosed, for example, inthe air supply duct of a gas turbine combustion chamber. It has alsobeen proposed to utilize the differential pressure between the fuelsupply duct and'the spill return duct to open the tip valve against thepressure of a spring tending to close it. The rating orstiffness of thespring must be such that the maximum differential pressure at which thefuel can be circulated when the tip valve is closed is less than theminimum pressure differential when" the burner is in operation. Sincethe latter'dilferential is quite low when the burner is operating atmaximum load, with the spill return duct closed or nearly closed,

the circulation of the fuel with the tip valve closed must be carriedout at a differential pressure which may 2,743,137 Patented Apr. 24,1956 ice of the space wherein it operates may lead to the opening,

of the tip valve when fuel is circulating under nonoperating conditions,with undesirable and even dangerous results.

The main object of the present invention is to provide an improvedconstruction for controlling the tip valve in a manner which avoids theabove-mentioned disadvantages of the previous proposals.

A specific object is to provide an improved liquid fuelatomizing burnerhaving a tip valve the position of which can be controlled bycontrolling the direction of flow of fuel through the burner. Anotherspecific object is to provide an improved apparatus of the typespecified wherein provision is made for reversing the direction of flowof fuel from the pump through the atomizing burner and back to thereservoir.

The foregoing objects are attained in accordance with the invention byproviding each liquid fuel-atomizing burner of the apparatus of the typespecified with a tip which may be integral with the valve or adiaphragm,

having movable surfaces disposed to act in opposition to each other ofwhich one face is exposed to a fluid, e. g., the fuel itself,substantially at the pressure prevailing in the fuel supply duct and theother to fiuid at substantially the pressure in the spill return duct,the vortex chamber being connected to the fuel supply duct and to thespill return duct by the passageways which inherently create a pressuredifferential whereby the downstream pressure is lower than the upstreampressure.

The composite apparatus, which may include one or a plurality of liquidfuel-atomizing burners as described in the foregoing paragraph, has aflow-diverting valve for each burner connected to the outlet of the fuelpump to permit the fuel under pressure to be directed at will eithertothe fuel supply duct or to the spill return duct of the respectiveburners; further, valve means (which may be a part of the aforesaidvalve or an additional valve connected for synchronous operationtherewith) are provided for each burner to selectively connect eitherthe spill return duct or the fuel supply'duct (whichever is notreceiving fuel from the pump) of the respective burner to an oilreservoir so as to maintain a complete circuit. A simple four-way valvemay serve both of the foregoing purposes. The valve thus permits theflow of fuel through the burner to be reversed. When the flow is in thenormal direction, that is from the fuel supply duct through the vortexchamber to the spill return duct, even a slight diiferential pressureserves to open the tip valve. When the flow is reversed, differentialpressure acts in the opposite direction and closes the valve. Hence, thepressure at which the fuel is circulated when the tip valve closes canbe as high as desired without incurrin any risk of opening the valve. 7

In order to hold the tip valve closed and prevent dribble from theburner orifice when'the' pump is not operating, the tip valve may beadvantageously provided with a light spring which is capable of holdingthe valve closed in these conditions. Such a spring will, of course, beconsiderably weaker than would be necessary to close the valve under anydifferential pressure encountered during operation of the burner.

The invention has the advantage that it lends itself to remote controlof the burner, and to individual or simultaneous control of a number ofburners. For simultaneous control, it is only necessary to arrange thatthe valve means shall be common to all the burners served by the samepump, or to one or more groups of such burners, while for individualcontrol separate valve means are provided for each burner.

The invention will be further described with reference to theaccompanying drawing forming a part of this specification and showing byway of example a preferred embodiment, wherein:

Figure l is a longitudinal section through a burner connected with avalve for reversing the flow therethrough; and

Figures 2 and 3 are flow diagrams showing the complete apparatus andillustrating, respectively, normal and reversed fuel flows.

Referring to Figure l, the liquid fuel-atomizing burner comprises anouter casing or hollow body 1 having a threaded cap nut 2 which retainsa flanged sleeve 3 and an orifice wall or jet plate 4 within and infront of the body 1, respectively. A valve member 5, disposed within thebody 1, comprises a tip valve 6, a hollow stem 7 and a hollow, enlargedpiston 8, the tip valve 6 being formed on the end of a rod 9 of reduceddiameter which is integral with the stem 7. The piston 8 has a closesliding fit in the cylindrical bore of the body 1 and the forward partof the stem 7 has a similar fit within the cylindrical bore of thesleeve 3, so that the valve member is capable of sliding axially withinthe burner.

The annular space 10 between the body 1, on the one hand, and the stem 7and sleeve 3, on the other, constitutes thefuel supply duct of theburner; it communicafes with a fuel supply pipe 11. Formed within thejet plate 4 is a conical swirl or vortex chamber or prechamber 12 whichhas a final orifice 13 and communicates with the fuel supply duct 10 byway of tangential swirl ports 14. The outer ends of these portscommunicate with an annular groove 15 formed in the rear face of theplate 4 so as to be always in communication with holes 16 formed in theflange of the sleeve 3 and arranged along a circle. projecting flange 17forming the rear wall of the swirl or vortex chamber 12 and providing acentral opening through which the rod 9 of the tip valve projects withan annular clearance 18.

The interior of the stem 7 and the piston 8 constitute the spill returnduct 19 of the burner, which communicates with the vortex chamber 12 byway of the annular clearance 18 and a plurality of holes 20 extendingthrough the shoulder formed by the junction of the rod 9 and the stem 7.The rear end of the spill duct 19 communicates with a discharge pipe 21by way of holes 22 in a cap 23 which closes the rear of the body 1 and agroove 22a formed in the body 1.

The pipes 11 and 21 lead to ports in a rotary, four-v way valve 24comprising a cylindrical body in which is rotatably mounted a valvemember 25. The latter has recesses 26 to 29, inclusive. Recesses 26 and27 are inter-connected by a bore 30 formed in the member 25, andrecesses 28 and 29 are inter-connected by a separate bore 31 also formedin member 25. The valve member can be rotated by a lever 32 between twoportions limited by stops not shown in the drawings. In the positionshown in Figure 1, discharge pipe 21 is connected by recess 26 with areturn pipe 33 which is provided with a spill control valve 34; andsupply pipe 11 is connected by recess 28, bore 31 and recess 29 with apipe 35 through which fuel under pressure is supplied from a pump. Whenthe valve member 25 is rotated clock-wise to its other position,in whichthe lever 32 occupies the position shown in chain lines in Figure 1,supply pipe 11 is connected by recess 27, bore and recess 26 with thereturn pipe 33; and discharge pipe 21 The sleeve 3 has an inwardly a thepipe 35.

is connected by recess 28, bore 31 and recess 29 with Thus, rotation ofthe valve member 25 has the effect of reversing the connections of pipes11 and 21 on the one hand with pipes 33 and 35 on the other, and thevalve is seen to be of the type adapted to connect the pipes 35 and 33to the pipes 11 and 21 selectively either in corresponding or reversedrelation.

As shown diagrammatically in Figures 2 and 3, the fuel-burning apparatuscomprises in addition to the liquid-atomizing burner indicated as awhole by number 36, a reservoir 37 containing liquid fuel, the spillcontrol valve 34, a, fuel pump 38 having the usual relief valve 39, andthe four-way valve 24.

Figure 2 shows the direction of fuel flow when the lever 32 of thefour-way valve 24 is in the position for operation of the burner. Inthis position, the fuel flows from the reservoir through a pipe 40 tothe pump 38 and thence through the pipes 35 and 11 to the fuel supplyduct 10 of the burner 36. From this duct, it enters the vortex chamber12 and a part of the swirling fuel emerges from the final orifice 13 asa spray 41, while the remaining part flows out through the clearance 18,holes 20 and spill return duct 19. This spill fuel, the proportion ofwhich is controlled by the spill control valve 34, flows by way of pipes21 and 33 back to the reservoir 37.

Figure 3 shows the direction of fuel flow when the lever 32 is in theposition for circulation of fuel flow when the burner is out ofoperation. In this position, the fuel flows from the pump 38 throughpipes 35 and 21 into the spill return duct 19 and thence forwardly intothe vortex chamber 12. The tip valve 6 being now closed, the whole ofthe fuel flows through the swirl ports 14 into the fuel supply duct 10and thence through the pipes 11 and 33 back to the reservoir 37.

With the fuel flow as shown in Figure 2, the differential pressurebetween the fuel supply duct 10 and the spill return duct 19, acting onthe piston 8, serves to hold the tip valve 6 in the withdrawn or openposition. When the fuel flow through the burner is reversed, as shown inFigure 3, the differential pressure, again acting on the piston 8,serves to hold the tip valve in the forward or closed position in whichit seats on the wall of the final orifice 13. Thus, with the lever 32 inthe Figure 3 position, as long as the pump 38 is operating the tip valveis held closed and fuel can be circulated freely at any desiredpressure, the latter being controlled jointly by the pump and the valve34. In order, however, to prevent dribble from the final orifice 13 whenthe pump 38 is not in operation, a weak compression spring 42 isprovided which urges the valve member 5 into the forward or closedposition. When the lever 32 is in the Figure 2 position, the tip valveis held firmly open at any operating fuel pressure, even at full burneroutput when the spill control valve 34 is nearly or fully closed, sincethe opening of the valve is opposed only by the spring 42, which israted to exert a pressure substantially below that due to the minimumoperating differential pressure between ducts 10 and 19. Instead ofplacing the spring 42, as shown in Figure 1, in an enlargement of theduct within the hollow piston 38, the spring may be situated in the duct10 or in any other convenient posi' tron.

I claim as my invention:

1. A liquid fuel-atomizing burner for spill return systems that havemeans for reversing the flow of fuel comprising: a housing having a fuelsupply duct; a prechamber communicating with said duct; an orifice wallforming a wall of said pre-chamber and containing a final orifice forsaid pre-chamber; a tip valve adapted to close said orifice; a spillreturn duct communicating with said preschamber and open for fuel flowin both directions; and means responsive to the direction of fuel flowthrough said open spill return duct for closing said tip valve upon flowof fuel in one direction and opening the tip valve upon flow of fuel inthe opposite direction, said means including a differentialpressure-responsive device having movable surfaces disposed to act inopposition to each other and exposed to fluid pressures substantially atthe pressures of liquid fuel in said fuel supply duct and spill returnduct, respectively.

2. A burner according to claim 1 wherein said surfaces havesubstantially equal areas and the tip valve is provided with a weakspring biasing said valve to closed position, whereby said valve isclosed when said pressures in the fuel supply duct and in the spillreturn duct are substantially equal.

3. A liquid fuel-atomizing burner for spill return systems that havemeans for reversing the flow of fuel comprising: a housing having a fuelsupply duct; a vortex chamber communicating with said fuel supply ductthrough one or more ports tangential to the axis of said chamber; anorifice wall forming a wall of said chamber and containing a finalorifice for said chamber; a reciprocable tip valve having a closedposition for closing said orifice and an open position; a spill returnduct communicating with said vortex chamber and open for fuel flow inboth directions; and means responsive to the direction of fuel fiowthrough said open spill return duct for closing said tip valve upon flowof fuel in one direction and opening the tip valve upon flow of fuel inthe opposite direction, said means including a movable member havingopposed surfaces exposed to fluid pressuressubstantially at thepressures of liquid fuel in said fuel supply duct and spill return duct,respectively.

4. A burner according to claim 3 wherein said housing has a cylindricalbore and said movable member is a piston reciprocable within said bore.

5. A liquid fuel-atomizing burner for spill return systems that havemeans for reversing the flow of fuel comprising: a housing having anaxial bore and providing a fuel supply duct; a hollow piston in the rearpart of the housing axially reciprocable within said bore having theforwardly facing surfaces thereof exposed to fuel in said fuel supplyduct, the interior of said piston defining a spill return duct that isopen at the rear of the piston, whereby the rearwardly facing surfacesof the piston are acted upon by fuel in the spill return duct; a wallstructure at the front of the housing defining a vortex chamber havingone or more ports tangential to the axis of the vortex chamber foradmitting fuel from the fuel supply duct tangentially into the vortexchamber; an orifice wall at the front of said vortex chamber having afinal orifice; an opening in said wall structure in rear of said vortexchamber, the front of said spill return duct being constantly incommunication with said vortex chamber through said opening for fuelflow in both directions; a stem at the front of. said hollow pistonprojecting forwardly into the vortex chamber through said opening with aclearance permitting the flow of fuel; and a tip valve at the front ofsaid stem situated to close said final orifice when the piston is in theforward position and retractable with said piston to open the orifice.

6. A burner according to claim 5 having a spring acting between saidhousing and the piston biasing said piston to forward position.

7. A burner according to claim 6 wherein the rear part of said spillreturn duct is enlarged in relation to the forward part and said springis situated within said enlarged part.

8. Apparatus for burning liquid fuel comprising: a source of liquid fuelunder pressure; a liquid fuel-atomizing burner having a fuel supplyduct, a pre-chamber with an orifice wall containing a final orifice, atip valve adapted to close said orifice, a spill return ductcommunicating with said pre-chamber, and a differentialpressure-responsive device having movable surfaces disposed to act inopposition to each other and exposed to fluid pressures substantially atthe pressures of liquid fuel in said fuel supply duct and spill returnduct, respectively, operatively connected'to said tip valve to close thetip valve when the fuel pressure in the spill return duct' exceeds thatin the fuel supply duct and to open the tip valve when the fuel pressurein the fuel supply duct exceeds that in the spill return duct; and adiverting valve adapted to connect said source of fuel under pressure atwill either to said fuel supply duct or to the spill return duct;

9. In combination with the apparatus according to claim 8, a liquid fuelreservoir; and valve means associated with said diverting valve forconnecting either said fuel supplyduct or the spill return duct,Whichever is not connected to said source of fuel under pressure, to thereservoir to discharge fuel to the reservoir.

10. Apparatus for burning liquid fuel comprising: a liquid fuelreservoir; a liquid fuel pump having the intake thereof connected tosaid reservoir; a fuel return pipe connectedto discharge oil into thereservoir; aliquid fuel burner having fuel supply andspill return ductscommunicating with each other within the burner, a wall structure at thefront of the burner having a final orifice, a tip valve for saidorifice, and differential pressureresponsive means responsive to thepressures of liquid fuel in said ducts adapted to open the tip valvewhen the fuel pressure in the fuel supply duct exceeds that of the spillreturn duct and to close the tip valve when the fuel pressure in thespill return duct exceeds that in the fuel supply duct; and valve meansadapted to connect the discharge of said pump and the said oil returnpipe selectively either to the fuel supply duct and spill return duct,respectively or to the spill return duct and to the fuel supply duct,respectively.

11. Apparatus for burning liquid fuel comprising: a diverting valve ofthe type adapted to connect a first pair of conduits to a second pair ofconduits selectively either in corresponding or reversed relation; aliquid fuel reset voir; a liquid fuel pump having the intake thereofconnected to said reservoir and the discharge thereof connected to saiddiverting valve as one of said first pair of conduits; a fuel returnpipe connected to said valve as the other of the first pair of conduitsand connected to discharge fuel into said reservoir; a spill controlvalve in said fuel return pipe for regulating the rate of fuel flow tothe reservoir; and a liquid fuel-atomizing burner comprising a housinghaving a fuel supply duct connected to said diverting valve as one ofsaid second pair of conduits, a vortex chamber communicating with saidfuel supply duct through one or more ports tangential to the axis ofsaid vortex chamber, an orifice wall for said vortex chamber containinga final orifice for said vortex chamber, a reciprocable tip valve forsaid orifice having closed and open positions, a spill return ductcommunicating with said vortex chamber and connected to said divertingvalve as the other of said second pair of conduits, and a movable memberhaving opposed surfaces exposed to liquid fuel substantially at thepressures of the fuel in said fuel supply and spill return ducts,respectively, operatively connected to said tip valve to move the tipvalve to closed position when the fuel pressure in the spill return ductexceeds that in the fuel supply duct and to move the tip valve to openposition when the fuel pressure in the fuel supply duct exceeds that inthe spill return duct, whereby said tip valve can be opened or closed atwill by operation of said diverting valve to flow liquid fuel throughthe burner in one direction or the other.

References Cited in the file of this patent UNITED STATES PATENTS

